Process of preparing printing members and product thereof



March 17, 1942;

G. s. ROWELL PROCESS OF PREPARING PRINTING MEMBERS AND PRODUCT THEREOF J Filed Nov. 17, 1939 2 Sheets-Sheet 1 INVENTOR. G EORGE. S. ROWELL v ATTORNEY.

March 17, 1942. G. s. ROWELL 2,276,594

PROCESS OF PREPARING PRINTING MEMBERS AND PRODUCT THEREOF Filed Nov. 17, 1939 2 Sheets-Sheet 2 FoG- INVENTOR. GEORGE S. FPQWELL ATTORNEY.

Patented Mar. 1 7, 1942 r urrs PROCESS OF PREPARING PRINTING MEMBERS AND PRODUCT THEREOF George S. Rowell, Cleveland, Ohio, assignor to George T. Trundle, as trustee, Cleveland, Ohio.

Application November 17, 1939, Serial No. 305,015

28 Claims.

This invention relates to a printing member of the planographic type and to a process of making such printing members. The above indicates the general object.

Other objects include the provision of a process of producing an improved planographic printing surface on malleable material, such as the metals aluminum and zinc; an efficient method of producing flexible planographic printing plates. or elements from strip or sheet stock; an improved manner of handling sheet or strip stock in the making of flexible printing members; an improved chemical processing treatment of grained planographic printing members; an improved manner of graining metal surfaces for planographic plate production; an improved manner of handling granular material to facilitate the forcible projection thereof onto malleable material to produce a grained surface thereon; an improved manner of controlling the grain or texture of printing surface on planographic printing members; a more economical and effective manner of making, assembling and protecting planographic printing members for storage pending eventual use, and the product or products of the procedures herein described.

A specific object is to produce a grained sur-' face on a suitable base, which surface has greatly improved qualities for enabling the retention of image or character forming means which are receptive to greasy printing media, such as lithographic ink, and further receptive to aqueous solutions on the non-printing portions to render them ink repellant.

Other objects and various specific advantages of the process and product will become apparent from the following description taken in connectionwith the accompany drawings. The drawings show preferred procedures in graining andotherwise preparing a planographic printing surface on sheet metal in long strip form. Individual sheets or plates would be similarly treated, except in the matter of feeding, which could be by the use of conveyor belts, sheet grippers on supporting drums, etc. Applicability of various features of the invention to the printing art in other ways, as in order to make non-flexiblesurface portions of strips (e. g.) of metal in the Cal first stage of graining treatment thereof, but varied relative to each other as will be hereinafter described; Figs. 3, 3a and 3b are views similar to Figs. 2 to 2b of the strip surface portions after a second stage of graining treatment; Fig. 4 is a magnified exemplary plan view of a small section of grained surface, at two stages of the graining process; Fig. 5 is a plan view, showing a satisfactory arrangement of nozzles for plate stock of average width; and Fig. 6 isa dia gram illustrating a device for throwing abrasive as from a nozzle with substantially uniform effective velocity entirely across-a strip in the process of being grained by percussive impact of granular material on the strip.

Lithographic printing using flexible printing members, e. g. thin metal strips or sheets (synonymous with plate in the usual sense) requires, particularly for large editions, a grain surface which will have long wearing life from the standpoint of image retention in definite areas and repellant qualities relative to printing fluid in other definite areas. Considerable variation in coarseness and fineness of grain is required for different uses (types of work) but the attribute of strength and long life in retaining the image definitely and fixedly in the image areas and in repelling printing fluid at definite and fixed non-image areas is always desired. The latter is more delicate or critical. alia, aims to enable as much variation in the type of grain surface as necessary while securing the element of strength, referred to above, irrespective of the type of grain surface required. The metals zinc and aluminum have respective attributes fitting them for use as planographic printing plate materials. Because of their differences I in corrosion resistance, hardness, etc., neither metal is ideal for use interchangeably in the different fields. The present invention tends to lend universal utility to these metals for planographic printing and enables the effective use of The above general discussion is principally in respect to graining the plate, which operation can be accomplished continuously on strip as will now be described. I

In Fig. 1 a supply of strip S is indicated at I, illustrating for instance, a roll of aluminum or zinc or any suitable alloy of either with other metals or materials), on an appropriate support. I prefer aluminum (termincludes aluminous alloys) over zinc, partly becauseof its greater The present invention, interresistance to corrosion and/or oxidation, and partly because it is harder or can be made harder in dense sheet form without becoming brittle at the surface, or at least can be made more resistant to wear and undesired shinyness, as by paper friction.

The strip as shown is suitably guided partially around a drum 2 having a uniform cushion surface, as of live rubber, thence across another similarly surfaced drum 3 and partially around the latter, and thence to a chemical processing apparatus, generally designated 4, to be described later.

Two separate steps of the graining treatment are accomplished on the convex faces of the strip as supported on respective drums. The first step is mainly one of raising minute grain projectioris on the face of the strip adjacent minute depressions cut therein, and for most satisfactory results requires a shorter radius of curvature on the drum. The second step which is mainly to peen and deform the projections, as will later be described, could be carried out effectively with the metal laid or stretched flat. The drum 3 is preferably about twice the size ofdrum 2. Both steps, however, can be performed effectively while the metal is supported on a single, curved surface as of a single drum or platen; for example a 10" to 12" rubber covered drum, this being the preferred size for this first step.

Beside the drum 2, at the left as shown, is a throwing mechanism or apparatus 5 for abrasive particles or granules, such as crushed sand, flint,

aluminum oxide, etc., the type being selected largely according to the desired use for the grained plates, the malleability and hardness of the material, etc. The abrasive can be thrown by fluid pressure, centrifugally or by impact force on the granules, and the term blast" used, for convenience, herein includes any suitable throwing means. Sharp abrasive granules are projected, as shown, from a nozzle l0 (preferably a battery of nozzles) which in cooperation with a constant well regulated pressure supply source is or are capable of continuously bombarding with abrasive a fairly narrow area circumferentially of the strip but as an ideal condition, with substantially uniform force and abrasive dis tribution substantially along the entire width of the stripeither instantaneously or progressively laterally of the strip. The strip is advanced at a uniform rate during the bombardment, as by continuously turning the drums, or one of them, or by appropriate strip or sheet feeding means not shown. The rate of advance is varied according to the efliciency of the equipment used for causing the bombardment of the strip by the ranules.

One manner in which a flat stream of abrasive can be secured by fluid pressure is by p p ll n the granules through a fiat nozzle. Greater uniformity of impact across the strip, when using a conventional nozzle in fixed position, can be secured by projecting the granules first against a deflector set at an angle to the axis of the nozzle. Also, whether or not such deflector is used, the'nozzle or nozzles can be moved back andforth across the work either by rectilinear movement without change in angle of projection relaw'tive to the work or by pivotal movement of the nozzle for sweeping back andiforth across the work as progressively advanced. jfn either case,

and nozzle.

cause this affords a better opportunity for spent granules to get out of the way of oncoming granules, and avoid being embedded into the strip by such oncoming granules. Granules which remain on the work or are embedded in the work after their force is spent lower the quality of product. It is therefore preferable that they be retained at a minimum. I I

Fig. 6 shows the nozzle 5 or 30 directed toward a deflecting plate I? set at-a-n appropriate angle relative to the nozzle and the strip S so that the abrasive grains, although emitted from the nozzle in conical form (as in case of a circular oriflce) are spread fanwise against the strip to be grained and thus, broadly speaking, are mainjtained at substantially uniform concentration per unit of area clear across the strip and more nearly at a uniform impingement angle. The deflecting plate I2 is preferably surfaced with high grade preferably hard rubber, so as to be highly wear resistant. The abrasive granules bounce off the deflector with very little loss in velocity and substantially at constant direction for a given relative adjustment of the deflector The deflector may be appropriately curved, further to secure'uniform distribution, in accordance with known laws of reflection.

An important feature both in respect to the first and second graining steps is the control of angles of projection of granules against the work as will be, more fully explained later. In the throwing apparatus as in Fig. 1 the angle of incidence of abrasive and work (see lines 23 and 24) can be controlled simply by adjustment of the nozzle about aconvenient center, as at l3. In Fig. 6 this control can be effected by adjustment of the deflector l2 or the nozzle, or the nozzle and the deflector. Additional guides and deflectors for the abrasive can, of course, be used for purposes of concentration of granules over limited areas on the strip. Lateral movement of 'the' blast across the work can be obtained by continuously oscillating the nozzle about an axis, such as indicated by the line (4.

In performing the first graining operation, the strip'is preferably supported on a curved surface of relatively short radius, this having been found much more effective than when the strip is flat or nearly flat. By way of explanation, the preferred angle of incidence between abrasive and work is a narrow acute angle. If the angle is about or nearly a right angle (as with the nozzle pointing at the drum axis) the surface of the strip is indented, but no proportionate high rims or peaks (terms used interchangeably with pro- Jections herein) are raised adjacent the indentations; undesirable permanent embedding of abrasive granules in the strip is apt to occur,and spent granules tend to oppose the action of oncoming granulesv (buffer action), thus reducing efllciency. In I my process, indentations are made but one of the outstanding characteristics of the first step is the throwing up of a comparable and usually greater number of projections above the eventual working surface of the strip or plate. With the strip or plate lying in curved form where worked upon, it is possible practicably to reduce the impingement angle nearly to zero. It is found that, with the work maintained in curved form,'spent granules are more effectively discharged and prevented from becoming embedded in the work by oncoming rapid lateral movement of the working portion of the spray across the work produces more univform graining than a. slow movement, partly beparticles. For the best results, especially for use with the finer classes of work, it is desirable that the angle should not approach zero to an extent duced with coarse sharp granules.

such that the abrasive tends to plow parallel furrows. However, such an application, even though producingiurrows, does not defeat the purpose as will become clear in connection with the description below of the second step (or series of steps) of the process. I

g The "abrasive is preferably controlled as to size, sharpness, velocity, and angle of projection against the work. In the first graining step, large granules of abrasive may be used for work requiring placement of the image as by lithographic crayon and generally for work requiring a coarse screen effect, e. g., poster work. Finer abrasive, properly controlled, ordinarily results in finer graining, suitable for example in fine screen photo-mechanical process work. Variation from coarse to fine graining with granules of constant size and abrasive quality can also be had by decreasing the velocity. Generallyspeaking, the deeper a given size of granule is forced into the work the coarser the graineflect wiL be on the work. Thus, coarse graining can be effected with fine sharp granules by increasing the velocity of impingement of the granules against the work. Conversely, fine graining can be pro- Thus, the ultimate result depends largely upon the velocity at which the granules strike the work, upon the angle of incidence of the granules with the work, and upon the sharpness of the granules. A few illustrations will sufiice to show the possibilities for variations in the grain effect obtainable in the first step.

For convenience, projection of abrasive approximately toward the axis of the drum on which the strip stock is supported (trajectory assumed as straight lines) will be referred to as projection at a direct angle, and projection toward areas considerably at one side of said axis as at a meeting angle.

Fig. 2 illustrates approximately the result of rapid projection of fine sharp granules about midway between a direct and the narrowest practicable meeting angle. Here, P is the normal (untreated) surface of the stock (extended for comparison as at p). Narrow pockets or indentations V are formed and relativelyhigh, closely spaced peaks M which rise above the normal or original surface of the stock. The

grained surface is both indented and raised relative to P. The metal is also probably torn to some extent, but not enough to detach the peaks from the stock. The inclination of peaks is due to the angle of ricochet of the granules.

The arrows indicate the angle of impingement of the granules with-the work. Zone 46 on Fig. 4

is typical of the relative arrangement of peaks as raised by the first graining step, viewed in The peaks are more or less parallel to plan. each other.

In Fig. 2a, a narrower meeting angle is -employed and the peaks are more inclined than This is far less satisfactory holding power for image and repellant, asshown at the left in Fig. 3b (zone 48).

Fig. 1 at the left illustrates diagrammatically one manner of controlling the coarseness and finenessof granules, and the velocities of impact on the stock. Here, [5 and I6 represent supply conduitsleading from tanks or hoppers supplied, respectively, say with fine and coarseabrasive granules.

The conduits have" control valves ll andlB.

I9 and are manipulatable (or the R. P. M. of a throwing wheelif' used). In'the particular arrangement illustrated, the

finer abrasive is admitted full flow (l1 fully open) to the ,IlOZZlG when the part l9.is adjusted for high speed of propulsionof granules,

' nozzle.

. the control elements l9 and 20 enables changes air valve 2| fully open; and coarse abrasive is at full flow (l8 fully open) when thepropulsive speed is increased as by opening the air valve f 22 of the coarse grain feeding portion of the Additional adjustment l9a and 20a in in speed of propulsion of the difierent classes of granules relative to each other, but at full or any desired partial flow of fine and coarse granules. Mixtures of coarse and fine abrasive at any desired proportions are thereby obtain? able for superimposition of fine graining on coarse, as above mentioned. I91: and 20a reprc sent adjustments in the connections l9 and 20 so that projection force and volume of abrasive can be varied relative to each other. 'The arrangement of nozzle units crosswise of the strip can be as indicated on Fig. 5.

The impact velocity of the abrasive granules on the work can in a given installation be governed by controlof air pressure as well known in sand-blasting. When a one-half inch round aperture is used in the nozzle and the nozzle is approximately 15 inches from the work, the average air pressure employed is around 10 to 15 lbs. per sq. inch, using up to 850 cu. ft. per min ute of compressed air. The pressure used should not be such as would tend to buckle'or distort the sheet itself (as distinguished from the surface or the sheet). It has been found that pressures of over 15 pounds can be used on thick plates, but tend to buckle and distort the same metal .005" to .010" thick which is the usual thickness range for small printing machines. Higher impact velocities can be used on thin metal passing over a curved surface without causing buckling and distortion than can be used on the same metal and thickness flat.

The throwing mechanism' 30 for the second step of the graining process may be essentially the same as the mechanism 5, and one nozzle alone can be used if properly manipulated.

More satisfactory and uniform work can be done by the use of a nozzle or set of nozzles 3| arranged to bombardthe strip somewhat inwardly from the-periphery of the larger drum' 3 as along the line 32, another nozzle or set of nozzles 33 pointed approximately at the drum axis as along the line 34, and another nozzle or set 35 oper ating nearer the roll periphery (nearly tangent thereto) as along the line 36. All of these nozzles can be arranged to oscillate rapidly back and forth as on pivot axes normal to the drum axis (see lines 31) to give a sweeping fire of blunt granules, or they can be set at diiferent cross fire angles and reciprocated rectilinearly back and forth crosswise of the strip S. The

noz zles 3|, 33 and 35 are also adjustable toward and away from the drum axis and are capable of being locked in adjusted positions, for instance in the illustrative positions suggested on Fig. l. The nozzles are supplied with granular material and pressure fluid in any known or suitable manner, the outstanding diiierence from the first graining step being that the granular material for the second step is selected for nonabrasive qualities, blunt or generally rounded grains or pellets being used. The size of grain may be variedas in the first graining step, like wise the force of impingement as by control of air pressure or other throwing force.

The action of the granular material on the work in the second graining step, as mentioned above; is a peening action, and, as illustrated by Figs. 3 to 3b, the projections or peaks M on the preliminarily grained surface are deformed (usually hooked) in such manner as to provide greatly enhanced holding power for moisture and in general for hydrophilic material with which planographic plates are usually, if not always, treated at non-printing areas, and greatly enhanced retaining power for image or character forming media on the printing areas.

With photo-litho methods in current use on conventionally grained plates, the sensitized image is held to the plate, largely if not entirely, by root portions of the image material occupying the indentations. These roots become more or less bulbous when a conventionally grained plate is treated after graining, as by passing it' through steel pressure rolls. A, characteristic of plates rolled after graining is that a top plane is established by the presence of plateaus resulting frequently in undesired bared metal at the top surface of the image. It is impossible to roll down a sand-blast or marble grained plate without crushing down and rendering ineifecin've the higher grain portions, if the lower portions are to be afiected at all. With the present process, the bombardment by thesecond step causes some action on all the preliminarily grained areas irre-' spective of height of projections. The smaller granules which are always present work on the smaller peaks through the interstices of the larger peaks. The present invention adds to such rooting of the image, as mentioned above, the locking action of the hooked projections, lending reater life and stability to the image, but with out tending to expose relatively large areas of metal at the top level of the image.

Fig. 3 shows at 5t (diagrammatically and greatly magnified) the appearance of the grain after the abrasive graining treatment already described (of. Fig. 2), and at St the result of bombardment of the peaks as by blast from the nozzle or nozzles 31. The angle of impingement of the blunt granules is indicated at 32 (cf. Fig. 1) The bombardment at this stage should have less force than that effected by the nozzle or nozzles at 35, otherwise the peaks or raised effects (may be ridges) are likely to be broken oil. Granules striking the sides of the peaks will turn the peaks sidewise and those striking centrally of the peaks turn them along the lines of impact. Thus the peaks or fingers raised by the first graining step tend to project in all directions and this efiect may be enhanced by cross fire from different nozzles orj-by sweeping fire from a. single nozzle.

Fig. 30. (at the right, zone 43) illustrates the result of projection of blunt granules from a more direct angle, as from the nozzle or nozzles 33 along lines 34. Here less pressure is employed than at either nozzle position 3| and 35. Too much bombardment force will crush the peaks down against the body of the strip or break them off. The direct impingement of granules tends further to mat the peaks, criss-crossing in all directions as illustrated at zone 41 on Fig. 4. The result of bombardment as by the nozzle or nozzles 36 which can be set to operate at nearly a tangent to the drum, 1. e. level with the strip area worked on, is to level and clean the grain and further crowd the peaks against each other or the curled ends thereof against the surface of the strip overhung thereby, giving the individual fingers and peaks support at two or more points. Greatest bombarding force can be employed in the peening treatment at the final stage i. e. greater than by nozzles 3| or 33.

It will be seen from the above thatthe range of angles which are employable for the'second (peening) step is greater than for the first step. In the first step there is an outer limit in respect to the meeting angle (suggested by the line 23) beyond which the cutting grains richochet or bounce off the work without producing deep pockets, although eiiective peaks may be raised by thefurrowing action above described.- The inner limit is reached when pockets only predominate. In the second step, the angle of projection of the blunt grains against the work is unlimited, assuming proper bombardment force is maintained. 4

A steady direct angle of fire in the second graining step would not ordinarily be employed as the initial treatment of the peening process, for then a considerable number of granules would strike between groups of peaks or projections and tend to produce dead spots. The tops of the peaks should be gradually turned. It should be emphasized that the peening treatment can all be done with one nozzle on a given width of strip. For instance, on 10" wide stock, three nozzles oscillated rapidly crosswise of the drum axis from lines of fire at 32 to the line of fire at 36 would approach an ideal arrangement.

Fig. 3b (somewhat larger scale than Figs. 2 and 241) represents at 'zone 68 the result of bombarding the work during the first step with coarse abrasive material mixed with finer abrasive material (or separately efiecting the two operations, fine after coarse). Smaller peaks and hollows M and V are thus imposed on the larger peaks and hollows M and V. The zone i9 is typical of the result of bombardment with blunt grains in the second step.

Referring further to Fig. 4, illustrating at 41 the matted and intermeshing effect of the second graining step on the peaks or fingers formed on the work, the peaks and fingers point in countless directions, forming in eiiect a Jungle of tiny, finger-like elements firmly anchored to the base (strip S) and more or less braced by each other and by the underlying base against dislodgment during the further treatment of the plate stock or handling of it.

The principal reason for operating on relative- 1y widely separated portions of the strip to effect thefirst and second graining treatments will be apparent from Fig. l. The abrasive material used in the first step (caught as by a collecting receptacle R) can be salvaged independently of the material (blunt grains) used in the second step (caught similarly as at R). Otherwise, the two materials could only be separated as to size. The material which becomes worn and electrical elements 58, and ting into suitable shapes blunted in the first stage can be used effectively in the second stage of the process. Crushed sharp sand should not be used in the peening step. Lake sand is very satisfactory, but round or rounded tiny pellets of any nature can be used, for instance, small glass beads or shot.

Those skilled in the art will perceive that the present grained plate in contrast to marble graining has been kept dry, whereas, usually, marble graining subjects the plate forcibly to moisture for forty minutes or more, probably penetrating the pores of the metal with moisture and other foreign matter tending to accelerate oxidation of the finished plate. The dry graining process, described above, necessarily removes oxide'scale,

. etc., leaving the strip or plate in an ideal con'dition to be treated, so as to render it permanently ready for use without requiring counter-etching. Such treatment can be carried out automatically in the preferred procedure (using continuously fed strip to avoid intermediate handling and marking), as follows:

After the second bombardment of the plate stock S described above, the strip is passed immediately to the chemical processing treatment (station 4, Fig. 1), as to a tank 50 (or spray) of quent exposure to normal oxidizing atmospheres. The washing does not remove the chemicalh' obtained protective film or buffer on the grained surface. Thus, the process is a considerable improvement over that followed (e. g.) with marble graining, where a counter-etching, as with acids, was necessary to remove oxides etc., followed by washing and drying and accompanying further oxidation during the drying period; it being well recognized that oxidation of metallic surfaces is promoted by the presence of moisture.

Since the plate of this invention is ready at subsequent times after preparation, as above described, for the acceptance of the printing image or characters without further prior treatment, not only is time and expense saved. but

use by careless or unskilled operators is not buffer or oxidation and corrosion arresting material. This preferably an aqueous solution of dipotassium phosphate (K2HPO4), which, at proper concentration, will, I have found, preserve the grained-plate indefinitely against oxi dation and other corrosive influences to which the plate is likely to be subjected even when mersion is ample where a 60% solution is used, and because the further treatment does not coat or corrode the grain, the immersion time can be increased as much as desired.

Alternatively, I can use the followingsolution, among others:

Ounces Ammonium fluorides 5 Ammonia 3 Water 128 The second formula is notas effective or as satisfactory in practice, the latter being due'in part to the difficulty in avoiding fumes and loss of ammonia by evaporation.

The strip next passes from the tank to dehydrator apparatus such as squeezing and blotting rolls 52, then is washed as by water spray at 54, further dehydrated as at 56, dried as by is then ready for cutand sizes for storage or immediate use.

When subjected to the above described chemical, etc., treatment, the planographic plates likely to impair sharpness of grain, whereas were a counter etching required to remove oxidation and other deposits, as heretofore necessary in actual practice, the corrosion of the acid bath frequently reduced the holding power of the plate (or, as known in the art, the platelost tooth), either through lack of proper skill or diligence. In the office devices field, the use of acids for counter etching greatly reduces the market, due to the fact thatsuch acids as required are dangerous to persons and personal property; increase employers"liability costs and require special expenditures for plumbing as a means for washing under readily available running water.

properly stored. The solution can be approxiright in Fig. l.

Ordinarily, plates are. stacked with their' grained faces adjacent paper separators, one of the latter for each plate. A considerable saving in production cost can be effected by carrying out the procedure partially shown at the lower This comprises performing the work above described simultaneously on two strips which are brought together, the second finished strip being indicatedat S, with both grained and chemically treated faces adjacent as when passed between assembling rolls 60. Si

multaneously, and at proper. speed, a separating web as of soft paper W isintroduced between the grained faces of the strips S and S as by rolls 6|. From this point the assembly of strips and separatorweb is conveyedto a shear or cutter,

- shown'diagrammatically as blades 62 and 63, and

the plates and separators are then stacked 'as in the pile or tier T adjacent the cutter.

By using the last described step of the process,

the manufacturer obviates practically all necessity for frequent handling of plates, as usually required, incident finger marking and waste of time, securing superior and less expensive plates.

I claim:

1. In forming a planographic printing surface on a printing member, the method comprising blasting one face of the member with relatively sharp granules directed toward said face principally at acute angles relative thereto, whereby to raise minute projections on the material of which the surface of the member is composed, then distorting the tops of the projections to cause them to overhang the member in slightly spaced relation thereto.

2. In forming a planographic printing surface on a printing member having a malleable faceportion, the method comprising mechanically treating said face portion generally all over the same in a manner to raise minute, closely spaced projections thereon and to form minute indentations adjacent the projections, and then mechanically distorting the free ends of practically all of the projections toward the" member to cause the projections generally to overhang the indentations in spaced relation thereto at substantially the entire portion which was subjected to the first mechanical treatment 3. In forming a planographic printing surface on a printing member, the method comprising raising above the normal surface of the material ofwhich the member is composed minute projections on said material, and then distorting the tops of the projections over the entire surface which bears said projections to cause the projections to overhang the member in slightly spaced relation thereto.

4. In forming a planographic printing surface on a printing member, the method comprising raising minute projections on the material of which the surface of the member is composed, then bombarding the surface of the member with a forced blast of granular material of such nature that it does not tend to cut the projections, said bombardment being directed laterally of the projections, whereby to distort the projections p in, a manner to raise peaks thereon, and then partially into overhanging spaced relation to the a surface.

5. In forming a planographic printing surface on a printing member, the method comprising bombarding the surface of the member with relatively sharp granules at an angle tending to raise projections thereon, and then bombarding the surface of the member with a forced blast in a manner to distort the projections partially into overhanging, spaced relation to the surface resulting from the first bombardment.

6. In forming a planographic printing surface on a printing member, the method comprising bombarding'the surface of the member with relatively sharp granules at an angle tending to raise peaks thereon,- and then distorting the tops of the peaks to cause them to overhang the member in slightly spaced relation thereto.

7. In forming a'planographic printing surface on a printing member, the method comprising abrading the surface of the member with sharp granular abrasive material and then bombarding the surface with a forced blast in a manner to distort the portions of the surface raised by the abrasive material but without cutting said portions to any substantial extent.

, 8. The improvement in forming a planographic printing surface, comprising relatively indenting and raising respective minute areas of malleable stock and then peening the raised areas of the stock to force portions thereof into overhanging but'spaced relation to the indentations.

9. The improvement in forming a planographic printing surface, comprising relatively indenting and raising respective minute areas of malleable stock and then blasting the stock to distort the raised areas of the stock to force portions thereof into overhanging but spaced relation to the indentations.

10. The method of graining flexible malleable sheet material to form a planographic printing surface thereon, comprising bombarding one face of the sheet with relatively sharp abrasive granular material while the sheet is supported on a curved surface, and then bombarding said face with relatively blunt or non-abrasive granular material.

11. The method of graining malleable sheet material to form a planographicprinting surface thereon, comprising bombarding one face of the sheet with abrasive granular materialprojected principally at an acute angle toward said face progressively bombarding the resultant face with granules projected at an angle to the principal axes of the peaks.

12. The method .of-graining malleable sheet material to form a planographic printing surface thereon, comprising bombarding one face of the sheet with abrasive granular material in a manner to raise peaks thereon, and then progressively bombarding the resultant face with granules projected in .cross fire relationship to each other against the peaks.

13. The method according to claim 12, wherein the second mentioned bombardment is partly at a narrow acute angle and partly at a less narrow angle.

14. The method of graining malleable sheet material to form a planographic printing surface thereon, comprising obtaining a coarse grain on one face of the sheet by bombarding said face with coarse abrasive, superimposing a finer grain on the coarse grain by bombarding the same with finer abrasive, and then bending the peak portions of the coarse grain into overhanging spaced relation to adjacent portions of the sheet.

15. The method of graining malleable sheet material to form a planographic printing surface.

thereon, comprising obtaining a coarse grain on one face of the sheet by bombarding said face face.

with coarse abrasive, superimposing a finer grain on the coarse grain by bombarding the same with finer abrasive, and then bombarding with nonabrasive granules the peak portions of the coarse grain to bend the same into overhanging spaced relation to adjacent portions of the sheet.

16. The method of graining malleable sheet material to form a planographic printing surface thereon, comprising progressively moving the material over spaced supporting surfaces, subjecting the sheet to bombardment with abrasive granular material while on one supporting surface, 'and then subjecting the grain raised by said bombardment to bombardment with blunt or non-abrasive material while on the other sur- 17. The method of graining malleable sheet material to form a planographic printing surface thereon, comprising progressively moving the material over spaced supporting surfaces of different curvatures, subjecting the sheet to bombardment with abrasive granular material while on the supporting surface having the smaller radius of curvature, and then subjectmanner that the peaks are bent out of parallel-- ism and generally into overhanging, spaced relation to the sheet.

'19. The method of graining malleable sheet material to form a planographic printing surface thereon, comprising bombarding one face' of the material with abrasive in a manner to raise peaks thereon which extend generally parallel to each other, and then bombarding the peaks with blunt or non-abrasive granules from a plurality of directions such that the peaks are bent out of parallelism and generally into overhanging, spaced relation to the sheet.

20. In graining malleable sheet material in forming a planographic printing surface thereon, the process comprising feeding coarse and fine abrasive granules to acommon discharge device and bombarding the sheet simultaneously with the same to impose fine indentations on the coarser indentations and raised effects accomplished by the coarse granules.

21. In graining malleable sheet material in forming a planographic printing surface thereon, the process comprising bombarding a face of the sheet with granules directed at an angle approximately normal to the sheet, then bombarding the face with abrasive granules at :a narrower angle to raise rim portions and peaks adjacent the indentations formed by the first bombardment, and then bending. the rim portions and peaks heterogeneously into overhanging spaced relation to the sheet. 22. In graining malleable sheet more direct angle relative to the area of the sheet bombarded, and then further bombarding the resultant grain surface with raking fire of non abrasiv'e granules. I

material in forming a planographic printing surface therehigh velocity, then at lower velocity from a 24. In graining malleable sheet material .in-

forming a 'planographic printing surface thereon, the process comprising graining-the sheet to raise minute closely spaced projections thereon and progressively moving the sheet along a predetermined path while projecting non abrasive granules onto the sheet from a nozzle whose axis moves rapid-1y back and forth across the path of progression of the sheet,

25. In graining malleable sheet material in forming a planographic printing surface thereon, the process comprising graining the sheet to raise minute closely spaced projections thereon 5 and'progressively moving the sheet along a predetermined-path while projecting non-abrasive granules onto the sheet from a nozzle whose axis oscillates across the path of travel of the sheet so as to vary the impingement angle of the granules at different areas of thesheet.

26. A planographic printing member of malleable material having, on one face, closely spaced relatively narrow projections with their free portions bent or hooked toward the general surface of the member and at least partly in r spaced relation thereto.

27. A planographic printing member of mal leable material having on one face closely spaced peaks with their free ends bent toward the said .face in various directions, and portionsintermediate to their free ends and base portions in spaced-relation to the body of the member in overhanging relation thereto.

28. In making planographic printing members,

the method of graining comprising projecting a stream of granular material against a deflecting surface set at an angle to the axis of the stream, whereby to redirect the stream and flatten the cross section thereof,- and placing the member to be grained in the way of the redirected granular material to grain the member.

. GEORGE S. ROWELL.. 

